1. Field
The present disclosure relates generally to mandrels and, in particular, to mandrels used in curing processes for forming composite structures. Still more particularly, the present disclosure relates to an apparatus, system, and method for forming a mandrel having voids configured to control expansion of the mandrel during a curing process.
2. Background
Mandrels are oftentimes used to form composite structures. As used herein, a “mandrel” is an object formed having a shape representative of a desired shape for a composite structure. A “composite structure”, as used herein, may be any structure or part comprised of composite material.
As one illustrative example, a composite laminate may be placed over a mandrel such that the composite laminate molds to the shape of the mandrel. The composite laminate may be comprised of any number of layers of composite material. Next, the composite laminate and the mandrel may both be cured such that the composite laminate consolidates to form a composite structure. The composite structure retains the shape of the mandrel even when the mandrel is removed. In particular, the composite structure may be hollowed inwards when the mandrel is removed. This hollow portion of the composite structure may be referred to as a “cavity” in some cases.
The mandrels used for forming composite structures may be formed from various materials. A mandrel may be formed from, for example, without limitation, a rubber material, a composite material, a metal, a dissolvable material, an elastomeric material, some other type of material, or some combination of the above.
In some situations, the material used to form the mandrel may respond to the heat and/or pressure generated during curing in an undesired manner. In one illustrative example, at least a portion of the mandrel may expand during curing and cause uneven pressure to be applied towards the composite laminate placed over the mandrel. The application of uneven pressure to the composite laminate may result in a composite structure that does not have the desired shape for the composite structure and/or that does not meet selected tolerances. In some situations, this uneven pressure may cause the shape of the cavity that is formed in the composite structure once the mandrel is removed to be distorted with respect to a desired shape for the cavity.
Consequently, a number of voids may be introduced into the mandrel when the mandrel is formed. These voids may help control expansion of the mandrel during the curing process such that substantially even pressure is applied to the composite laminate during curing. These voids may need to be formed within selected tolerances to provide the desired expansion control. However, some currently available methods for forming these voids within a mandrel may be unable to form voids having dimensions within selected tolerances.
For example, some currently available methods may use extrusion techniques to form these voids. Extrusion may include pushing or drawing the material for the mandrel through a die of the desired shape having the desired cross-sectional profile. However, some currently available extrusion techniques may be unable to form voids having dimensions within selected tolerances.
Other currently available methods for forming voids may use molding techniques. Molding may include using a die to mold the mandrel and then extracting the die from the molded mandrel. However, this extraction may be more difficult than desired. Further, the extraction of the die may cause one or more undesired inconsistencies to be formed on or in the mandrel.
In this manner, the currently available methods for forming mandrels having voids that use the above-described extrusion techniques or molding techniques may be unable to form a mandrel that meets selected tolerances. Additionally, some currently available methods for forming voids in mandrels may be more expensive and/or time-consuming than desired. Therefore, it would be desirable to have a method and apparatus that takes into account at least some of the issues discussed above, as well as other possible issues.